Oven of the direct-flame continuous-tunnel type



Sept. 9, 1930.

J. WILLIAMSON 1,775,302

OVEN OF THE DIRECT FLAME CONTINUOUS TUNNEL TYPE Filed Nov. 7, 1927 6 Sheets-Sheet l Sept. 9, 1930. J. WILLIAMSON OVEN 0F THE DIRECTJ FLAME CONTINUOUS TUNNEL TYPE Filed Nov. 7, 1927 6 Sheets-Sheet Sept. 9, 1930. 1,775,302

ovEN 0F THE DIRECT FLAME CONTINUOUS TUNNEL TYPE J. WILLIAMSON VFiled Nov. '7.

1927 6 Sheets-Sheet ,l ff

Sept. 9, 1930. J. WILLIAMSON a 1,775,302

OVEN 0F THE DIRECT FLAME CONTINUOUS TUNNEL TYPE Filed Nov. 7, 192'? 6 Sheets-Sheet 4 SCP- 9, 193D-v J; WILLIAMSON 1,775,302

OVEN. OF THE DIRECT FLAMEVCONTINUOUS TUNNEL TYPE Filed Nov. 7, 1927 6 Sheets-Sheet 5 Sept. 9, 1930. J. WILLIAMSON OVEN 0F THE DIRECT FLAME CONTINUOUS TUNNEL-TYPE' Filed Nov. '7, 1927 6 Sheets-Sheet 6 l l l Patented Sept. 9, `193)y UNITE rar Friet i OVEN oi tennisser-ranura continuons-TUNNEL TYPE 1 imputation mea November 7, les?, serial up. attrae, and in` @metv Bmainfneeember e2, 192e.

This invention-consists ci improvements-in or relating to ovens ofthe. direct flame continuous,tunneltype suitable forthe firing' of pottertiles,bricks, pipes and othersiinilar *5" Ware, or the heattreatmentV of other materials.` a Y One ohjectlo'f `the invention is so to 'construct'anoven of the type referrcd'to that Haine canphe inadeto talle various qcourses l throughthe'goodsto suitvarying require inents,"that is to" say, to travel `upwards or downwards, or `horizmtally` in a transverse direction,`or` horiontally in a longitudinal or in a'diagonal direction, and also to alternate *l5 `from one side of theloven tothe other, giva ing` direct Contact of thetlameto all parte of lthe `truck on Whichgoods are placed', at the same time utilizing the 'hot exhaust, gases 1` for'indirect heating of the goeds in the earlv *'20 stages of firing, thustending te greater regie larity ofteinperature `than hitherto attained iii ovens of the direct Haine type. i

`.Another object lof the invention is so to construct a continuous tunnel oven of the di-V 7-*2-'5 rect flame type that the goods can he heated indirectly by the products of'comhustion, up to or-heyond the `stage ivvhere the water of chemical"comhinationis given oil, in apurely oxidizing atmosphere, and that the vapour *F19 thusjproducedncan he' taken avvay as it is formed, thus preventing` cracking, scumining, and'other defects Von the goods which are coinxnonfin other'ovensivl'iere the preheating is done hy direct Contact of thcexhaust gases witlithe goods.y Y

`Another bjectof the invention is so to construct aytunnel oven Voi the direct flame type, that air from each end thereof can hev circulatedthrough it in-'a helical or screw fm like direction towardsA the furnace Zone, so

asto enahlethe heating and cooiing,.h57 radiation, conduction and convection, to he eleeted s, inalinore coinpletenianner than is n'owdone in "thefusualftype'of direct ilameoven. i

`Another`ohject`of theinvention is so to constructa tunnel oven that `.the rate of coolingcanhe accelerated or retarded at any par-` ticularfpoint'iii the cooling process, and that s the heat given upV can be utilized to provide 'Clsu pplementary hot-air for combustion of fuel vsection taken on the line and to provide thesnecessary power required to Worlr` the systenior plant so as to provide an almost complete thermal system. s 4

`An0ther ohject oilthe invention is soto construct .a tunnel oven. that a current of air can hefinadeto flow between the haseof the trucks carrying the goods `and the rails on which the trucks run, so asto keep the hearings, rails,` and lower hricltwork of the `oven cool in the `furnace Zone. .s

A further object `of theinvention is so to construct a tunnelwoven of the direct fla-inc type that salt glazing or `other similar processes can he carried outina continuous or in an intermittent manner, that is to say, in a glazing' atmosphere in themfurnace Zone all" the time, or'alternating from anoxidizing to a glazing atmosphere as the goods travel through this zone, .and so that' the salt used can he distributed in an effective manner and the amount thereof regulatedV to suit require ment. ,s Y s For attaining the ahove'inentioned objects a direct flame continuous oven embodying` the invention, is constructed as shown in the accompanying drawings, `a longitudinal sec tional elevation whereof is represented by tin.- three parts Figs. l, l@ and lb, Figs. 2, 2a. and 2b, being corresponding sectional plan views. Figs. 3 to 9 inclusive *are transverse sections j taken on the lines II'IhIIlito IX-IX ref 'spectively, appearing in Figs.

2, 2a and 2b. 3fL is a detail view showing a incdiiication. Fig. lO is a horizontal section ot one halt of the firing zone of the-oven and an adjacent recuperator,to a larger scale than the corresponding portion of the oven shown in Fig.' 2a, thesection Correspondingl to the line X-X of Fig. l2. Fig.` il is a vertical Eil-Xl of l0. Fig. 12 is an external Aelevationot` the same portion of the oven with recuperator. Figs. 13, and l5 are cross sections through the furnace Zoneof modified constructions of the 1 oven.

` Asshown in Figl ltowlQ inclusive, the

s oven comprises vesuccessive zones, namelg7 preheating, heating l equalizing, `furnace" AandA cooling .Zones lettered respectively A., 13,0, D and E 'through which the goods to he fired,

SUG

placed either in containers, or uncovered, upon trucks, are caused to travel slowly, entering at the preheating end A and leaving at the cooling end E as is usual.

The portieri of the oven constituting the furnace zone D is provided at a number of points along each side thereof with burners, the burners being separately controlled by dampers so that a very long soaking heat is obtainable in this zone. The said furnace zone which may advantageously be arranged more or less centrally of the length of the oven can be heated either by the combustion of gas, or oil, issuing from ports or nozzles, or by the combustion of solid fuel on open fire-gratos. In the example illustrated, the heating is ell'ected by the combustion of gas each burner, located at 1, (Figs. 2, 3, 11 and 1Q) being constituted by ports 2 leading from two long gas ducts 3 and ports t leading` from a number of short air ducts 5 the gas and air ports being controlled by dampers 6 and 7 respectively. Along each side of the furnace zone and at points that are below the perforated platform 8 of each truck 9 are also provided a number of outlets 10 through which, after the flame has done its work on the goods G under treatment, the resulting products of combustion can escape into side flues 11 arranged at opposite sides of the oven. These side fines are in communication with other side fines 11"' 11", 11C extending` from the furnace zone D through the portions C, B, A of the oven constituting the equalizing heating and preheating zones of the oven and finally communicate with the external atmosphere, either by way of a chimney 12 (Fig. 1), or through a fan 13. ri`he fines 11 at opposite sides of the tiring zone D are adapted to be heated by radiation and conduction from the incomingflame playing on the outside of he lines and also it may be by heat from supplementary burners arranged inside them so that the products of combustion can be again raised in temperature before entering the fines 11a traversing the heat equalizingzone C. The supplementary burners for each lue 11 are constituted as shown in Fig. 2, on the right hand half of 3, and in Figs. 10, 11 and 1.2. by gas ports 14;, each communicating with the corresponding gas tine 3 below, and air ports 15 each communicating by a vertical air flue 15X with a longitudinal overhead hot air flue 16. f he supplementary gas and air supply passages may advantageously have associated therewith separate valves or dampers 14; and l5 to control the supply of and air therethrough so as to enable the goods under treatment to be fired in various ways. Y

Conveniently, the combustible gas supplied to the main and supplementary gas ports 2 and lll, may Je obtained from an independent gas producer, the gas being fed into a ,soa

duct 17 (Figs. 1a and 3) and thence to the main ducts 3 which may be arranged in the foundation of the oven, as shown, or in any other convenient position. The air supplied in the main and supplementary air ports 4 and 15 is heated in the manner hereinafter described.

iiir is drawn into the oven from each end thereof, and travels towards the furnace zone D. The air entering` the inlet end portion of the oven is heated by the hot exhaust gases flowing through the exhaust tlues 1lb and 11c and used for preheating goods admitted to the oven and in part is further heated in the heating zone B by the exhaust (fases flowing through the flues 1lb, and used for expelling water of combination in clay goods and for combining with and removing any carbon from such goods. These portions of heated air are, after use, drawn off by a fan or a chimney and may be utilized for heating parts of the factory, if required, or for generating steam. Other air admitted to the heated portion of the oven after becominff heated thereby, is used for supporting combustion of gas at the main and supplementary burners. The air admitted to the cooling zone of the oven is used for cooling the heated goods. Part of it is caused to circulate in a helical manner through side flues 18 and the interior of the cooling zone so as to come in contact with the goods intermittently, the air there by heated being ire-cooled by other air that flows through tubes traversing the flues and is afterwards used as supplementary air for the burners, as hereinafter described.

rlfhe side flues may be of any desired scction but may advantageously be of approximately triangular shape as shown. Their walls may be plain in section, or of cavity, or honeycombed type, but in order to produce a large heat absorbing and radiating surface they are preferably made with honeycombed surfaces inside and out. The side tlues 11. 11 and 11" in the furnace, equalizing and heating zones D, C, B respectively are made of good refractory material having a high ratio of conductivity, whilst the falls of the flues 11O of the preheating zone A, may be made of material of a lower refractory character but of `greater conductivity, such as cast iron or other suitable material being shown in Figs 2 and 7 as eonstituted by a-pair of iron pipe runs at each side of the oven.

Opposite the flue tubes 11c at each side of the preheating zone A is arranged a screen wall 19 (Fig. 7) of heat insulating material, so as to shut off radiant heat from the fines to the goods, and transverse walls 20 1 and '2) are placed between this screen and the adjacent side wall of the oven at intervals apart equal to one or more truck lengths, so as to form a series of separate compartments around the lues 11 at each side of the oven.

The `arrangement is such that air. admitted to thebottorn of the first compartment@ at eachside ofthe oventhrough an opening at 22v` under thecontrol, it may be, of; a damper23, can pass froinone compartment to the other by convection, the air entering the bottoni of the first compartment .n then iioWing round passage at 26 (Fig. 1.);and a flue 27 (Figs. 1,

6 and?) the-fan 13er chimney 12. n'lhe first chamber wat each side 'of the oven may take air from the interior of theoven through an opening inthe screen 19 instead or from" the `surrounding atmosphere through. the opening 22, as described,: the airV travelling infeach` case .through the compartments @my and oven in a helical course, and in thevsaine direction .as the trucks travel. A

In the heatingzoneB, the goods are heated by radiation from the Walls ofthe fines 11b and by conveeted air currents and as the vapour from the Water of combination in the goods .is given` ohit isndrawn into the overheadflues 27` throughopenings v28 formed inthe Vault ofthe oven and controlled by dampers 29, theloverhead iiuebeing in coinmunication with the chimney 12, orfan 13. Or, if ldesired, the vapour ladenV air may be drawn `from thebottoxn-of the truck through portholes 11d (Figs. land 6) in the inner" Walls of the side'lue's 11b andthence be dis charged? into the external atmosphere, as

throughv the ilues 112110.V 4Theiport holes 11d are ,controlled bydarnpers .116, vone of which isfshown in Fig. 6,'capable otbeing operated through openings llfin theouterwalls of the Oven aUdaligned.holes in the outer Walliof the flues 11b. a.- y

InV the heat equalizing Zone C, the side fluesl Haare, as shown in Fig. 5, o'f'larger cross' section than the other fines, so as to present a "greaterheatradiating surface and atthe Sametime allowthe hotproducts of cornbus?4 tion thereintofexpandfreely. `Vhere"great regularity of temperature is required, such iiuesjllarnay.l be connectedto an overhead flue 30 (Fig 5) forming a double vaulted connnon chamber extending over'thef-itruch or-truclrs in the "form of `afniuille so that the goods will be heatedbyfdirect radiation from the hot Wallsbehind which the hot exhaust gases travel, and as the Water` of combination has been driven out of thegoodsin the 'previousy Zone `B, the'goods are here 'graduallyraised in" temperature untllithey reach the furnace or direct flaruezone D; The lues .11a may,

as shown inFig.` 5, beprovided With chequer- A y f 11, 11F, 11at the saine sideof the oven to the vWork division Walls.

31 and 32 are damper-controlled air and gas inlet ports constitutingburners by which the lues 11a can be independently heated. 33 and 34, Figs; 2a, 10, 11 and 12, are damperswhereby the llues 11 can be isolated from the fines 11a; 35 and 36, Figs. 2 and 6, are `dampers Wherebyues 11a can bel placed in co1n. rnunication With Zone C, and 37and 38, Figs. 2 and 7 are danipers whereby communication between the lues 11c and the chi1nney12 or fan 13 can be interrupted. f

In the furnace zoneD, when firing with a descending fla1ne,the combustible'` gas and` airare causedlto enter the oven on each side through the openings 2 and Lland combustion takes placeV in the space 'formed between the inain Walls 39 (Fig. 3) of the oven and the side lues 11, each burner at lbeing separated from itsneighbour by a `dividing Wall ll0 (Figs. 2a and 10) so as to form a separatel combustion space for the gas to burn in. `The i` dividing Walls 40 are so arranged as to forni between both `pairs thereotfa gradually inf. creasing space proceeding upwardly, and thus"v to cause the ianie to assume a fan-like shape before it reaches the goods. As the spacing ot the dividing Walls() may be Inade equal to the lengt-h of a truck, asheet of flame of this length entersthe oven from each burner at each side thereofand risesto thervault Wherev the iames from opposite sides meet and immediately equalizein temperature. `The combined flame then descends through the goods G and passes through andunder the perforated truck platform `8 and enters the` lll() side lues 11 through the port holes 10 in the` l inner side Walls thereof and traverses` the remaining flues 11a, 11b, 11c to atmosphere; Ey-jrneans ofthe series or dani Ders rer ferred to, iaine issuing from the various burners can be caused to travel: through the goods Gin any of the directions hereinbetere mentioned. Thus, Within the fines 11 Vin `the vfurnace zone'D, iarne may also beproduced by the burners constituted by the air and Vgas supply ports 14, 15, and by closing onef ieri of the dampers 33 and 341- between the 'fines 1.1;,V and-11a on one side ofthe oven, say the dainperj 34, opening the other damper, say 33, and:

openingtheigas and air vdanipers` G and I? controlling the supply` oiI gas and aiuto the ports 2 and 3 of the main `burners and thoseA controlling the supply of air and gas through i the ports 1% and 15 to the iiue 11 onV the side of the oven at which the `closed valve itis-gary located, flame can be producedoutside and j Within the said iiue andbe caused to pass` respectively over thewtlue `and through the port holes 10 vinv the iue and travel across the,` y

oven` and the.truclrtherein.and` he goods in `atransveise direction and enter the,opposite` sideA flue 11 through the port holes 105 there` in.- Theproducts fot' clonilnistion` can then, travel through thelatter flue 11` and the rlues liv end of the oven and into the external atmosphere if the corresponding exhaust valve 3T be open and the other exhaust valve 38 be closed. If both exhaust valves are open half of the products of combustion can pass from the one side flue 11 through the overhead connecting flue 30 (Fig. 5) to the opposite flue 11 so that the products ot combustion will then flow simultaneously through the fines 11, 11b and 11C at each side of the oven to the external atmosphere.

By closing the dampers 33 and 34 between both side flues 11 and 11a and opening the two dampers 35, 3G arranged between the side flues 11, 11b, between the heating Zone B and equalizing zone C, the flame from all the burners at each side of the furnace Zone can be caused to travel in a horizontal longitudinal direction through. the goods in the equalizing zone C until it reaches the ports controlled by the said dampers 35, 36 where the products of combustion will be caused to pass into the side flues 11" of the heating zone B and thence through the flues 11c into the atmosf phere as before, if both exhaust valves 3T and 38 be open.

It will be obvious that by alternately opening and closing the exhaust dempers 37, 38 arranged at the fan or chimney7 end of the oven, and leaving the other dampers and 36 as they last were, flame can be caused to travel through the furnace and equalizng zones alternating from one side of the oven to the other. Likewise, by closing the l dampers 35, 36 and again opening dampcrs 33, 34 and alternately closing and opening the exhaust dampers 37, 38 before, the flame will reverse from one side of the oren to the other, travelling in a horizontal transverse direction across the furnace zone D.

In the cooling zone E, immediately adjacent the furnace zone D and in the same line as the exhaust fiues, and on each side of the oven, is a recuperator 42 comprising chequer brickuf'orlr (Figs. 1, 2a, 4, 10, 11 and 12) through which air can be caused to flow, the choquer work being heated by the goods during cooling thereofvand whilst they are passing between the recuperators. The heat of each rccuperator is given up to air which enters through a valve controlled transversely arranged inlet passage 42, then flows through a longitudinal passage 42h below the recuperator 42 to a chamber 42C, then through the recuperator to a rear chamber 42d up which it flows and thence enters the rear end Vof the overhead hot air flue 1G hereinbefore referred to. From this flue the hot air can be supplied to the main and supplementary burners hereinbefore described and throuf'h ports 16a to the oven chamber over tl ne ifltes 11. Air is or may also be supplied to cach recuperator 42 from other sources ashereinafter described.

Extending from this air heating and goods cooling Zone to the eXit of the oven, the oven is made of a narrower cross section (Figs. 2b and 11). In this portion of the oven the last stage of cooling is effected, partly by air in direct contact with the goods, and partly by air in indirect contact therewith. By a systcm of tlues and dampers, the goods in any particular section of this Zone can be cooled quickly or slowly. When cooling the goods by air in direct Contact therewith, the cooling may, as shown in Figs. 11 and 9, be effected on the thermo-syphon system, by passing the hot air from the cooling goods through the tubes 44 of a vessel 44a around which cold air or water is caused to circulate, the hot air from the oven after lbeing thus cooled, returning to the oven to be again heated, and so on, 45 and 46 representing air inlet and outlet passages connecting the interior of the tubes to the interior of the oven. Or cold air may be drawn direct into the oven, as through a number or" openings 47, controlled by dampers 47n (Figs. 1b and 2) passed through and over the goods and discharged into the external atmosphere through valve controlled openings 48 in the roof of the oven, which openings lead to a flue 49 and chimney 50.'

vWhen cooling by indirect methods, the cooling is effected by radiation and conduction,`

the section of the zone being of muflle construction, the inner walls of which may be constructed of thin material of high conductivity behind which air is caused to flow. Thus, referring to Figs. 1", 2b and 9, each of the flues 18, which extend along part only of the length of the cooling Zone E, is divided into a number of compartments by vertical transverse division plates 18a and traversing the said compartments, are air tubes 18b through which cold air is caused to flow from the external atmosphere. oven communicates with the said compartments through top and bottom openings 52 and 53, so that air heated by contact with the goods enters the compartments by the top ports 52, is cooled by the tubes 18b and reenters the oven by the bottom ports 53, the air thus beingl caused to circulate through the heated goods andcooling compartments in a helical direction along the cooling Zone and in an opposite direction to the travel of the goods. The cooling air enters the tubes 18b through a damper controlled opening 51 (Figs. 1a', 11 and 8). The other ends of the said tubes can be placed in communication with the overhead flue 49 through a by-pasrs duct 49a controlled by a damper 49b (Figs. 10, 11 and 12), so that the air heated in the tubes 18? can be delivered into the external atmosphere. Or by closing the damper 49", and opening a damper 49, )reviously closed, the heated' air leaving the tubes 18b can be directed into the flue 42D, below the corresponding recuperator 42, and the chamber 42, then through the recuperator,wherein it The interior of the .sec

will be further heated, andfthence be delivered through chamber 42d into the corresponding overhead hot air flue 16. l

When goods being iiredrequire salt glaz- Y u lated at will. The saltis immediately volatilized by and mixes freely with the flame which then reachesthe goods, the salt coinbiiiing with the silica in the vclay thereof and forming therewith a glaze on the` goods. The exhaust gases, pass under the .truck platform and entering the `side flues 11, pass away to the external atmosphere as before, so that the on-cominggoods do not come in contact with any salt fumes until they have reached a teinperature high enough to bring Vabout the chemical change.

For distributing the salt, there may be arranged in the walls of the oven, in close proximity to thefinain burners, or some `of them ea-rthenware pipes56, inside each of which is a screw conveyor 57 driven at any speed to `suit requirement. "Immediately over the conveyors is a hopper 58 containing the salt, and as the conveyors revolve slowly the salt is conveyed through the pipes and discharged through passages 56` on to thetop of the side liues 11 inside the oven in such a position that the flames pass through it, carrying itforward to the goods as hereinbefore described. Or,l as shown in Fig. 3a, the salt may be dis tributed to the burners by chutes 59 connected to hoppers 6() inside each of which` is ar Vranged a druni 61 having a series of blades or paddles arranged round its circumference. The arrangement is such that as each pair of blades comes under the hopper, a quantity of salt enters the drum, and as the drum revolves slowly, the salt is dischargedinto the chutes 59 leading to the burners, the salt being finally discharged, as before on tothe top of the sideflues 1l or in such other position that the flame will carry it forward to the goods.

Instead of distributing, the salt as here-` inbefore described it may bevapourized in a separately heated vessel and the vapour passed into the furnace through the oven flames.

The following arrangement may be ado it ed for cooling the trucks. Fixed to opposite .sides of each truck base 9' are metal plates 62, hereinafter called apron plates, and resting on the floor of the oven are longitudinally arranged channel plates 63, which are filled `with sand and extend from one end of the oven to the other, so that as the trucks travel along the oven, the apron plates 62 dipinto the sand and vform an ef` iicient seal, isolating Athe upper portion of the oven from the lower portion, as is usual in otherV types of tunnel ovens. rails 64; in thebase of the oven on whichtlie trucks travel, arearranged pipes v65 (Figs. 2a

and 3) throughgwhich air or steannor both,

under pressure, is or are caused to flow, these pipes extending to a point beyond the furnace Zone D. At intervals in the furnace Zone, these pipes are provided with a series of outlet branches 66 each discharging into an open ended bent pipe 67 of much larger diameter.

@ne end of each of thesebent pipes is`con-` nectedto the corresponding `air flue 5, the other Yend of the pipe communicating with the space underneath the truck.` The ar-` rangement is such that the pressure of the air discharged from the outlet branches A66 into the bent pipes 57, induces a flow of air to take place underneath tlietrucks,;on the same principle as a steam and water injector, this air then entering the flues in the brickwork and in cooling the latter becomes heated and is used for supporting combustion, as

hereinbefore described. The air inlet pipes` 65 may, as shown in Fig. 10, be extended beyond the .furnace zone `l) and air be caused to issue from each of them through an outlet (ltrL into one end of a bent pipe 67a` thecther end of which opens into the aforesaid flue ft2" of the corresponding recuperator 42, so that the air escaping from such outlet 66EL will induce hot air to flow from below the. goods Gr into the corresponding recupei'ator and thence into the overhead hot air flue 16, this supplementary air being afterwards used for supporting combustion at the main and supplenientary burners. Thus, it will be seen that the recuperators Ll2 may receive air from three different sources. Het air may alsobe delivered from the overhead yhot air ilues 16 through outlet 16a and thence over the fines 11 `to the interior of the oven..A

Fig. 13 shows how the furnace `zone portion of the oven can be modified to adapt it for working with upwardly `moving flames.` For thisI purpose the oven is provided on' each side, at each burner position, and below the side flues 11, with ports 68 through each of which gas and air suppliedthrough `the Fig. 14 shows a modification of the con` struction shown in Fig. 1-0, suitable for use Between vthe ceV where the lateral space for the oven is limited. In this case the side iiues ll are each made of rectangular cross section, its outer side wall being formed by the corresponding side wall 70 of the oven and the top of each flue is in communication through openings llX with a iiue 7l formed between the roof 72 of the oven and a lower crown or roof 73. The latter is provided with a longitudinal row of outlet openings 74 through which upwardly liowing flames and products of comhustion can pass from the furnace Zone into the flue 7 (l and thence to the side tlues ll..

F ig. 15 shows a inodiiication of an oven for producing downwardly moving flames, suitable for use where the lateral space for the oven is limited, the section being taken through the oven in different transverse planes. In this case each side Aflue, ll is also of rectangular shape and has the outer wall constituted by the adjacent side wall 7() et the oven, as in Fig. 1l, but it has inlets il* at its lower end for flame and products of combustion. Also, the gas from each side main 3 is supplied at each burner position through a damper controlled passage if in the corresponding side wall 70 oi the oven to a combustion chamber 7 5 formed between the top wall 72 of the oven and a lower crown or roof 7 3 and into which air is also supplied from each side main 5 through a conduit 4X extending upward through the correspoiuling side flue 1l. The flame resulting from the combustion of the gas and air in the chamber 75 passes downward through holes 76 in the crown or roof 7 3 and through the goods G in the furnace Zone the products combustion entering the side iiues ll through the low r inlets ll therein. In this case, glazing salt may, when required, `be dropped from salt distributing means 60, (il and 5f) through the holes 76 in the crown 73 and into a. receptacle 77 carried by the goods and be vapourized by the flame presentA The arrows in Figs. 13, 1.4 and l5 indicate the direction of flow of the gas, air, thune and products of combustion.

At the inlet end of the oven, in each case, the hot exhaust gases may be passed through a water tube boiler before reaching the atmosphere. By means of a separate pump the hot water from the hot water heater 44-44Cl (Figs. 1b and 9) is pumped into the boiler where it is converted into steam, this steam being afterwards used for driving a turbine er other engine for propelling the trucks through the oven for driving the fan to withdraw exhaust gases, and for supplying steam if required, for the gas producer. In this way, practically the whole of the heat in the system can be utilized, except that lost ey radiation, which is reduced to a. minimum by an eiiicient system of insulation, thus eifecting a very large economy in fuel.

l. In a direct flame tunnel oven, a furnace Zone for goods, having at each side thereof a number of burners and a flue, the burners being arranged to deliver iame into the furnace Zone between the side lues and the side walls of the furnace Zone and the side tlues being` in communication with the furnace Zone, and means whereby flame is enabled to take various courses longitudinally and transversely through the goods.

2. In a direct flame tunnel oven, a furnace zone for goods, having at each side thereof, a number of separately controlled burners adapted to deliver flame into the furnace Zone, and a flue in communicatie-n with the furnace Zone, and one or more supplementary burners arranged in each tlue.

3. In a direct thune tunnel oven, a furnace zone for goods, having at each side thereof, a number of separately controlled burners adapted to deliver flame into the furnace zone`y and a flue in communication with the furnace zone, and one or more supplementary burners arranged in each flue, each of the latter burners comprising gas and air ports in the floor of the flue, and separate gas and air ducts for delivering gas and air to said gas and air ports.

4. In a direct flame tunnel oven comprising s preheatmg, heating, equalizmg and furnace zones through which the goods to be treated successively pass, tlues arranged at each side of each of the said Zones, the flues being normally in communication with each other, andv the flue at each side of the furnace zone being in communication with that zone, and means for separately controlling the flow of hot gases through each set of side flues.

5. A direct ame tunnel oven according to claim 4, wherein the side lues at opposite sides of the equalizing zone are in communication with each other through an overhead iiue.

6. A direct flame tunnel oven according to claim 4, wherein the side lines at opposite sides of the equalizing Zone are in communication with each each other through an overl'iead ilue and each of said flues is provided with controlled gas and air ports to form burners whereby the said tlues can be heated.

7 A ldirect flame tunnel oven according` to claim 4, wherein the roof of the heating Zone is provided with valve controlled outlet apertures for moist air and with an exhaust duct with which said apertures can `be placed in communication and which adapted to be placed in communication with the external atmosphere.

8. A direct flame tunnel oven according to claim 4, wherein the roof of the heating Zone is provided with valve controlled outlet apertures for moist air, and with an exhaust air duct with which said apertures can be placed in communication and which is adapted to he placed in communication with the external atlim llo

i 9; A direct flame tunnel oven comprising preheating, heating, equalizing, furnace' and cooling zones through which goods tonbe treat- 4ed successively pass, flues at opposite sides of the preheating, heating, equalizing and furnacezones, theset of fines at eachfside ofthe oven being normally in communication with onealnother7 the flues at each side ofthe furnace Zone being in communication with that exhausting means connected to the exit ends of the flues at opposite sidesof thepreheating Zone, dainpers adapted to close the communication between the lues at each side of the furnace and equalizing Zones, damper controlled inlets whereby the flues at `opposite sides of the heating zone can be placed in communication vwith that zone, means for separately controlling the communication between the exit ends of each set of lues and the exhaustin g means, burners for delivering Aflame into the furnace zone from opposite sides thereof and supplementary burners within the flues at opposite sides of the furnace zone. l0. A direct flame tunnel oven according to claim 9, wherein the fiues at opposite sides of the equalizing zone are in communication with each other through an overhead flue.

ll. A direct flame tunnel oven according to claim l, wherein the side flues at opposite sides of the preheating zone", consist of two sets of tubes of good heat conducting materia-l, longitudinal screens arranged at opposite sides of the said Zone and each adapted to form with the corresponding side wall of the oven, a chamber through which the corresponding set of tubes extend longitudinally and transverse walls arranged between each screen and the corresponding side wall of the oven and adapted toV subdivide the corresponding chamber into a series of vertical compartments the first of whichyat the inlet end of the oven, is adapted to be placed in communication with a source of air supply, and an exhaust flue in communication with the llast compartment, i said screens Vbeing formed with upper and lower openings arranged to enable air to circulate through the said compartments and the preheating Zone in a helical manner, substantially as described for the purpose set forth.` l

l2. In a direct flame tunnel oven, a fur-` nace zone having at each side thereof a num- `ber of gas burners and a line in communication with the said furnace Zone, each burner comprising valve controlled gas and air ports and a combustion chamber in communication with the furnace zone, gas ducts each common to all the gas supply ports at one side of the furnace zone, a number of air ducts at each sideof the said zone, each conimunicating with one of the air supplyports at the corresponding side of the oven7 a number of compressed air supply pipes extending along the floor of the oven below trucks carrying goods and each provided with outlet branches and pipes of larger diameter than said t branches and into which lthe said branches can deliver compressed air, said pipes being each in communication at one end with the spaccat thebottom of the oven below the truckstherein and at the other end with oneof the hot air ducts connected to Y l l vthe gas supply port of a burner.V Zone through openings in their inner walls, u

13. In a direct flame tunnel oven, afurnace zone for goods, having ateach side thereof,` a number of separately controlled main gas burners with combustion chamber adapted to deliver flame into said furnace Zone and a flue in vcommunication. with said Zone, a

adapted to be connected to the air supply ports of the supplementary burners.

. 14. Ina direct flame tunnel oven., heat rei cuperators arranged at each side 0f thecooling zone of the oven and immediately adjacent to the furnace zone, each recuperator comprising a chamber charged with chequer briclrwork and having a valve controlled aii inlet passage leading to one end thereof and a hot air outlet passage at the other end thereof and an overhead hot air flueextending from the hot air `outletpassage longitudinally of the corresponding side of the oven, adjacent tothe oven. u

l5. In a direct llame tunnel oven, heat refurnace Zone of the e cuperatorsarranged at each side of the cooling Zone of the oven and immediately adJa- `cent to the furnace Zone, eachreculierator comprising a chamber charged with choquer bri clworl; and having a valve controlled inlet passage leading to one end thereof and a hot air outlet passage at the other end thereof,

an overhead hot air flue extending from the l hot air outlet passage longitudinally of the corresponding side of the oven? adyacent to the furnace zoneof the oven7 and compressed airisupply pipes extending along` the floor `of the oven to the furnace zone and there connected to the air inlet ends of the two recuperators. y A u j 16. In a direct flame tunnel oven, air cooling meansarranged above the coolingzone of the oven and near to the furnace Zone of the oven7 the said cooling means comprising a Y vessel traversed by a number of tubes around Which a cooling medium can be caused to flow, and air chambers located at the opposite ends of the tubes and communicating with the interior of the cooling zone at different points in the length of the latter.

17. In a direct flame tunnel oven, a cooling zone having at each side thereof, for part of its length, a goods cooling arrangement comprising a number of vertical compartments formed b v and between the adjacent side Walls of the cooling zone, the adjacent side Walls of the oven and a series of transverse vertical divisions, and air tubes extending longitudinally through the compartments and transverse. divisions and adapted to be placed in communication with the external atmosphere for admittance of cool air, the inner Walls of said compartments being formed with upper and lower air inlet and outlet openings arranged to admit of air heated by goods in the cooling zone, passing into the upper portions ofthe said compartments, and after descending over and becoming cooled by Contact with the air tubes passing through said compartments, re-entering the lower portion of the cooling Zone and again coming in contact with the heated goods.

1S. In a direct 'dame tunnel oven, a goods cooling arrangement at each side of the cooling Zone of the oven and for part of its length, cach cooling arrangement comprising a series of vertical compartments the inner Walls of which, forming part of the side Wall of the cooling zone, has upper hot air inlets and lower cool air outlets communicating With the cooling Zone, and cold air supply tubes extending horizontally through the said compartments, a valve controlled air inlet connected to said tubes, an overhead hot air eX- haust flue at each side of the cooling zone, a heat recuperator arranged at each side of the cooling zone, adjacent to the furnace zone of the oven, and having a valve controlled inlet passage for admission of cool air to one of its ends, and a hot air outlet passage at its other end, an overhead hot air flue connected to said hot air outlet passage and extending along the side of the oven adjacent to the furnace zone portion thereof, and means whereby the hot air leaving the said tubes can, at will, be directed into the corresponding overhead exhaust flue or into the corresponding recuperator.

19. In a direct flame tunnel oven, a furnace zone having at each side thereof, a number of gas burners and combustion chambers, and a flue having in its inner Wall a number of openings in direct communication With the furnace Zone, the combustion chambers extending upward between each flue and the adjacent side of the oven and communicating with the interior of the furnace Zone over the top of the Hue, means for delivering salt for glazing goods in the furnace Zone on to the top of the flue, and cars' adapted to pass through the tunnel, each car being provided With a perforated platform for supporting the goods, this platform having a space beneath it which as the car moves along comes adjacent the aforesaidv openings, whereby the products of combustion carrying the glaze will pass down through the goods and the lfoles in said platform and thence into said Signed at Hamworthy, Poole, Dorset, this 21th day of October, 1927.

' JOHN WILLIAMSON.

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